The idea came as a comparison of di-hedral vs an-hedral in fixed wing aircraft. Anhedral is always unstable as the rolling axis is below the dynamic cg of the aircraft. Where high wing dihedral aircraft usually have the rolling axis above the dynamic cg.
Uhh, that's not why airplanes with dihedral are more stable than airplanes with anhedral. You need to research how real aircraft fly, not RC models. The truth is out there.